MONTHLY PRECIPITATION SUMMARY
Hawaiian Islands
MONTH: April 1998
PREPARED May 1, 1998
State:No significant Flash flooding was reported. Significant drought
conditions continue across the state.
Below average precipitation occurred state wide with all first order
and 58 automated rain gages receiving less than average rainfall in
April. Hawaii has four first order National Weather Service Offices
and 69 automated rain gage stations. This continued the seven month
trend state wide of drier than usual conditions. A major
consideration in things returning to closer to average conditions is
that April is the end of the wet season and average rainfalls in many
locations on the islands go below 1 inch per month.
During much of April 1998, a ridge of high pressure that had been over
and west of the islands shifted north of the islands at all levels of
the atmosphere. This allowed the surface high northeast of the
islands to strengthen to nearer to average position and strength. This
shift in weather patterns came with the shift to the spring season and
has brought stronger trade winds and thus trade wind showers to the
windward sides of the islands. This added rainfall in windward areas
has helped relieve some of the very dry conditions there. However,
much more rainfall is needed to get beyond the longer term drought
situation.
Island of Kauai:
Most reporting stations had just at or below average precipitation for
the month. The most negative anomalous precipitation pattern in the
month of March occurred on the north and northeast sides of the island
with only 33 to 72 percent of average rainfall in those areas. Kokee
on the northwest side of the island received the greatest amount of
precipitation for the month, 12.04 inches which was 177 percent of
average. This is one of the favored locations for trade wind showers
with winds blowing just a little east of northeast. The south side of
the island received significant rainfalls this month mainly from being
in the favored location for trade winds blowing around the south side
of Mt. Waialeale.
Island of Oahu:
Below average precipitation again occurred this month at most
locations. Areas in the central portion of the island were the
exception with above average rainfall. Trade wind showers that
developed on the Koolau mountains moved on down wind to the west
southwest depositing significant rainfall in the central portions of
the island and on the northeast facing sections of the Waianae
mountains. Leeward areas were again below average as frontal systems
that pass through or near the islands at times in April did not
materialize. The greatest negative precipitation anomaly was along
the southwest side of the island, in the area known as the Waianae
area (leeward of the Waianae Mountain range) where only 14 percent of
average (.23 inches) precipitation occurred. Even though rainfall did
increase in windward areas, most locations still were below average as
this is one of the wetter months of the year.
Maui County:
Molokai and Lanai were below average at reporting stations with Lanai
City receiving 61 percent of average rainfall (2.13 inches). The
Island of Maui reporting stations indicated below average
precipitation at all but one location. Negative anomalies were
particularly noted in the areas with dependence on synoptic scale
precipitation in April, such as Lahainaluna, Kihei and Ulupalakua.
This continues the several months' period of very dry conditions in
those areas. Zero to 42 percent of average rainfall occurred in those
areas this month with rainfall amounts of 0.00 at Kihei to 0.71 at
Lahaninaluna. The running nine months' rainfall total for Kihei has
only been 1.83 inches, which is 12.9 inches below average.
Hawaii County:
A wetter precipitation pattern was noted on the Big Island with all
windward areas coming much closer to average precipitation than in
previous months. This is one of the areas where the return of trade
winds and showers were significant in helping relieve some of the
drier conditions in the state. The areas in the Kohala mountains,
have not suffered as greatly from dry conditions through the winter,
received well above average rainfall in April. It appears as though
when the trade winds are a little east of the average trade wind
direction, which appears to have occurred frequently in April, this
area is favored for precipitation. The Kina side of the island starts
becoming more dependent on convective precipitation at this time of
year. Weather patterns didn't favor afternoon convection and a good
set up of sea breezes in those areas and precipitation was well below
average at all reporting locations in those areas. Waiaha, not far
from and up slope of Kailua - Kona Town, was the station with the
greatest negative precipitation anomaly with only 25 percent of
average or 1.59 inches of rainfall.
Below are statistics and part of a Public Information Station.
THE FOLLOWING ARE RAINFALL STATISTICS FOR SELECTED LOCATIONS
AROUND THE STATE AND COMPARATIVE DATA. THE ISLAND AND STATION
NAME ARE LISTED WITH THE MAY 1998 RAINFALL TOTAL. FOR COMPARISON...
THE AVERAGE FOR THE MONTH AND PERCENT OF AVERAGE ARE LISTED FOR
THE STATION IN THE FOLLOWING TWO COLUMNS. LONGER TERM STATISTICS
ARE LISTED WITH FEBRUARY... MARCH AND APRIL THREE MONTH RAINFALL
ACCUMULATIONS... AVERAGES FOR THOSE THREE MONTHS AND PERCENT OF
AVERAGE FOR THE THREE IN COLUMNS FIVE... SIX AND SEVEN.
Data units are inches.
Kauai Apr 98 Ave Pct Ave Feb-Mar-Apr Ave Pct Ave
Lihue 1.83 3.50 52 4.34 11.00 39
Hanalei 8.07 12.70 64 14.51 36.80 42
Hanapepe 2.84 2.20 129 3.77 8.40 45
Oahu
Honolulu 0.54 1.50 36 0.78 5.91 13
Waianae 0.23 1.60 14 0.38 6.40 6
Hawaii Kai 0.45 2.20 20 1.49 9.30 16
Manoa Lyon A. 12.06 13.00 93 20.46 37.60 54
Waialua 1.08 2.80 39 1.96 10.50 19
Ahuimanu 3.12 9.90 39 7.78 23.50 33
Molokai
Kaunakakai 0.19 1.20 16 1.01 5.60 18
Lanai
Lanai City 2.13 3.50 61 4.88 11.30 43
Maui
Kahului 0.97 1.80 54 1.64 7.40 22
Hana 2.33 9.00 26 3.96 25.30 16
Kihei 0.00 1.20 0 0.09 5.50 2
Lahainaluna 0.71 1.70 42 1.16 6.80 17
Wailuku 1.44 3.00 48 5.24 13.60 39
Hawaii
Hilo 8.86 15.30 58 18.34 39.50 46
Pahala 0.43 5.00 9 0.82 17.40 5
Honaunau (Captain Cook
2.12 6.10 55 4.02 14.40 28
Kamuela 14.26 6.90 207 20.10 20.80 97
Kamuela (Higher Elev.)
16.59 6.90 240 24.90 18.70 133
Laupahoehoe 14.62 18.90 77 23.72 51.60 46
Sources: First order climate network weather observations stations of
the National Weather Service at Lihue, HI, Honolulu, HI, Kahalui, HI,
Hilo, HI. Additional data were taken from the HYDRONET state network
of automated rain gages. Data collected in the automated gages are
not certified and information used above should be used for
information purposes only.
Roger V. Pierce, Senior Service Hydrologist
National Weather Service Forecast Office
Honolulu, Hawaii